usb: gadget: bind UDC by name passed via usb_gadget_driver structure

Introduce new 'udc_name' member to usb_gadget_driver structure.
The 'udc_name' is a name of UDC that usb_gadget_driver should
be bound to. If udc_name is NULL, it will be bound to any
available UDC.
Tested-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/udc/udc-core.c

@@ -549,21 +549,35 @@ EXPORT_SYMBOL_GPL(usb_udc_attach_driver);
 int usb_gadget_probe_driver(struct usb_gadget_driver *driver)
 {
 	struct usb_udc		*udc = NULL;
-	int			ret;
+	int			ret = -ENODEV;
 
 	if (!driver || !driver->bind || !driver->setup)
 		return -EINVAL;
 
 	mutex_lock(&udc_lock);
+	if (driver->udc_name) {
+		list_for_each_entry(udc, &udc_list, list) {
+			ret = strcmp(driver->udc_name, dev_name(&udc->dev));
+			if (!ret)
+				break;
+		}
+		if (ret)
+			ret = -ENODEV;
+		else if (udc->driver)
+			ret = -EBUSY;
+		else
+			goto found;
+	} else {
 		list_for_each_entry(udc, &udc_list, list) {
 			/* For now we take the first one */
 			if (!udc->driver)
 				goto found;
 		}
+	}
 
 	pr_debug("couldn't find an available UDC\n");
 	mutex_unlock(&udc_lock);
-	return -ENODEV;
+	return ret;
 found:
 	ret = udc_bind_to_driver(udc, driver);
 	mutex_unlock(&udc_lock);

include/linux/usb/gadget.h

@@ -1012,6 +1012,8 @@ static inline int usb_gadget_activate(struct usb_gadget *gadget)
  * @reset: Invoked on USB bus reset. It is mandatory for all gadget drivers
  *	and should be called in_interrupt.
  * @driver: Driver model state for this driver.
+ * @udc_name: A name of UDC this driver should be bound to. If udc_name is NULL,
+ *	this driver will be bound to any available UDC.
  *
  * Devices are disabled till a gadget driver successfully bind()s, which
  * means the driver will handle setup() requests needed to enumerate (and
@@ -1072,6 +1074,8 @@ struct usb_gadget_driver {
 
 	/* FIXME support safe rmmod */
 	struct device_driver	driver;
+
+	char			*udc_name;
 };